Consider the following explanation: (1) George took his umbrella because it was just about to rain. This is an explanation of a quite distinctive sort. It is profoundly different from the sort of explanation we might use to explain, say, the movements of a bouncing ball or the gradual rise of the tide on a beach. Unlike these other types of explanations, it explains an agent’s behavior by describing the agent’s own _reasons_ for performing that behavior. Explanations that work in this way have a number of distinctive and important properties, and we will refer to them here as _reason explanations_. Looking at the use of reason explanations with a philosophical eye, one is apt to experience a certain puzzlement. One wants to know precisely what makes a given reason explanation true or false. So, for example, the explanation given above seems to be saying that George’s reason for taking his umbrella was that it was just about to rain. But what exactly makes it the case that this is George’s reason? Does he have to actually be.